One wall of a half pipe.
A halfpipe divided in half lengthways and used for a single, often massive, aerial trick.
A smaller version of a half pipe.
A halfpipe that has been divided in half length ways to create a segment that skiers and snowboards can approach at a speed, and will be launched into the air to perform a single, aerial trick. 
A halfpipe with only one wall. It looks like a snow sculpted shape which contains a transition and a vertical, and is used as a jump to catch air.